All species face adaptive problems that need to be solved in order for an organism to survive an reproduce. One of most important adaptive problems that species must overcome is predator avoidance because an organism cannot pass its genes to the next generation if it is killed. Despite a significant database concerning the presence of predator detection and predator response mechanisms in non-human animals, there is a dearth of evidence regarding how they might operate in humans. The current proposal focuses on this issue by investigating the existence of predator detection mechanisms in young infants. The main hypothesis of the proposed studies is that infants possess a psychological mechanism that provides a perceptual template, or minimal representational description, of animals that were threats to our hominid ancestors - in particular, snakes and spiders. The proposal brings together diverse methodologies to examine this question. One series of studies will examine whether neonates and young infants preferentially orient toward schematic and real-images of spiders and snakes. The relative contributions of cortical and subcortical structures to these behaviors will also be explored. A second series of studies will use the familiarization procedure to provide converging evidence by investigating whether young infants categorize dangerous animals as equivalent and as different from non-threatening animals. This approach to a core question in cognitive science represents a new discipline of scientific endeavor in developmental evolutionary psychology. The results will shed light on the role of innate and learned mechanisms in human behavior and will have relevance to cognition, development, evolutionary psychology, clinical psychology, and neuroscience.